Nullsoft went back to Nitrane after 2.22 because people complained it was too slow (Nitrane trades off accuracy for speed).

Thanks; found that on Bouvigne's web site, too.

Also, upon further research (also on mp3tech.org), only versions prior to 1.9 of FhG suffer high frequency errors described above; version 1.9 (e.g. in K-Lite codec pack 2.47+) does not have this problem. I had an older version installed; I'm not sure which version is supplied with WMP.